1. Field of the Invention
The present invention relates to an image blur prevention apparatus for preventing image blur which is caused due to camera movement.
2. Related Background Art
There have been proposed a number of apparatuses which are intended to prevent failures in photography due to camera movement by detecting a vibration due to camera movement, displacing a correction lens in response to the detected value and correcting a variation of an optical axis of an image. More specifically, these apparatuses are arranged so that the vibration is detected by a vibration sensor such as an angular acceleration meter or an angular velocity, an angular displacement is electrically or mechanically calculated in accordance with a signal from the vibration sensor, and the correction lens is driven in accordance with this angular displacement information.
Methods of correction by the correction lens include parallel shifting or tilting of the optical axis for some of the photographic lenses, or a combination of parallel shifting and tilting of the optical axis and provision of a variable angle prism (VAP) in a front part of a photographic optical system.
The following particularly describes the method of shifting some of the photographic lenses. This method is adapted so that a correction lens frame is held to be freely slidable either in a pitch direction or in a yaw direction at right angles to the optical axis for a circuit base member by holding a coupling member on the circuit base member of an image blur correcting unit to be movable in a direction (for example, the pitch direction) at right angles to the optical axis for photography and holding the correction lens frame on which the correction lens is mounted on the coupling member to be movable in a direction (for example, the yaw direction) at right angles to the optical axis.
As an actuator for driving the correction lens, a voice coil is fixed to the correction lens frame respectively in the pitch and yaw directions at right angles to the photographic optical axis, and a pair of a yoke and a magnet corresponding to these voice coils are fixed to the circuit base member.
For detecting a shifted position of the correction lens in the pitch and yaw directions, respectively, a light emitting device (or a light receiving device) is held on the correction lens frame and the light receiving device (or the light emitting device) corresponding to the light emitting device is held on the circuit base member to detect the position of the correction lens in response to a quantity of received light from the light emitting device whereby the correction lens is accurately driven and controlled according to this positional information.
In an electrical wiring for the above, a printed circuit board provided with a control circuit for driving and controlling the correction lens is mounted on the circuit base member, an IRED which moves for the circuit base member and the coil serving as the actuator are wired with thin conductors between electrical components and the printed circuit board, and the lengths of conductors are determined with an allowance enough to meet the maximum extent of movement of the correction lens frame, thereby ensuring stable electrical connection for relative movement of the components. In addition, instead of a plurality of conductors, the apparatus is arranged so that electrical connection is made with a U-curved flexible printed circuit board.
In the above conventional example, however, the printed circuit board mounted on the circuit base member and the electrical components such as the IRED and coils, which are relatively moved, have been connected with conductors and therefore the number of man-hours for assemblies such as soldering work and costs have increased. The number of conductors has also increased with variations in their properties and therefore a possibility of breakage of these conductors during assembly would be higher. In addition, it has been troublesome to repair individual conductors.
Wiring with the flexible printed board has been disadvantageous in that the width of the overall pattern of the curved part of the board is excessively large if the wiring patterns are arranged in one assembly, an energizing force by curving the flexible printed circuit board is strong to impede the movement of the correction lens frame and the driving force is changed by a curving direction of the printed board and adversely affect the control as a whole.